1. Field of the Invention
The present invention relates to a rodless cylinder, and more specifically to a rodless cylinder wherein the load applied to a sliding table which is disposed outside a cylinder and displaced in accordance with the reciprocating motion of a piston, can be dispersed and supported on the cylinder side, thereby making it possible to smoothly move the sliding table in accordance with the reciprocating motion of the piston.
2. Description of the Related Art
A rodless cylinder has recently been used in various ways as a workpiece feeding device in a factory or the like.
The rodless cylinder can have a reduced stroke as compared with a cylinder with a rod coupled thereto. Thus, the area occupied by the rodless cylinder is small and the rodless cylinder is easy to handle. The rodless cylinder can also prevent dust or the like from entering as compared with the rod-coupled cylinder referred to above. As a result, a highly-accurate positioning operation can be effected. The rodless cylinder normally comprises a cylinder body having a slit defined therein so as to extend along the longitudinal direction thereof, and a sliding table. A piston loaded into the cylinder body is formed integrally with the sliding table by a connecting member.
This type of rodless cylinder has been disclosed in U.S. Pat. No. 4,373,427 or DE-PS 3,124,915, for example. In particular, the rodless cylinder described in DE-PS 3,124,915 is constructed such that a guide groove is defined in a given portion located outside a cylinder tube and a guiding means mounted to a leg which extends toward the given portion from the ends of the sliding table, is fitted in the guide groove. According to DE-PS 3,124,915, when a lateral force is applied, the guiding means is held against the guide groove so as to avoid an increase in width of a slit.
According to DE-PS 3,124,915, however, the leg should be disposed so as to extend toward a position far spaced from the outer side of the cylinder tube as seen from the sliding table and to hold the guiding means.
When the guiding means is fitted in the guide groove upon application of the lateral force under this construction, one end face of the cylinder tube, which defines the slit, forcibly approaches the other end face of the cylinder tube, which defines a slit on the opposed side. Thus, the inside diameter of a bore defined in the cylinder tube is reduced as a whole so that a piston is forcibly inactivated. That is, the piston stops moving when the lateral force is applied. In other words, a workpiece feeding operation is unexpectedly stopped, thereby causing a problem in that a workpiece held in engagement with the sliding table cannot be smoothly fed.